Map of long walls of China in 220 BCE
The "long walls" in China, 220 BCE.
Click on image to enlarge it.

The Zhou (Chou), Yan (Yen), and Qin (Chin) walls were built by the Zhou, Yan, and Qin states, respectively, between circa 300 BCE and circa 240 BCE. Most of the First Emperor's Great Wall, constructed in 214-210 BCE under the supervision of General Meng Tian (Meng T'ian), probably incorporated these Zhou and Yan Walls. Most likely, he renovated and fortified these walls and filled in gaps. Whatever the First Emperor and Meng Tien built to extend these walls have been so worn down over the centuries that almost nothing remains of them. The First Emperor's Great wall was built of compacted earth, not stone or brick. It should not be confused with what is so well known today as the Great Wall, though in some places the two overlap. The stone wall popularly known as the Great Wall today was built during the 16th century.